Bacterial vaginosis (BV) is the most common vaginal infection worldwide and the most common cause of vaginal irritation, discharge and malodour. It is estimated that the prevalence of BV is about 30% in the United States, 44% in sub-Saharan Africa and about 10% in Australia. BV is linked to serious health problems such as preterm birth, post-operative infection and increased susceptibility to HIV and other sexually transmitted infections.
While BV has been studied for many years, its cause remains unknown and treatments available are not always effective. BV is characterized by an imbalance in vaginal flora in which normally plentiful Lactobacillus spp. are scarce and other anaerobic bacteria, such as Gardnerella vaginalis, Mobiluncus spp., Atopobium vaginae and Prevotella spp. are plentiful.
Current treatments recommended for treatment of BV include metronidazole, clindamycin and tinidazole. However, these treatments are becoming less effective because of resistant bacteria and also have significant side effects. Metronidazole and tinidazole carry a potential risk of carcinogenicity and also cause nausea, abdominal cramps, vomiting, headaches and flushing if alcohol is consumed during treatment or for up to three days after treatment. There is also a high incidence of fungal infection, such as Candida albicans (Thrush), during antibiotic treatment of BV. Furthermore, clindamycin creams are formulated with mineral oils unsuitable for use with latex condoms or other rubber products such as diaphragms and therefore may require abstinence from sexual intercourse during treatment to avoid pregnancy and/or infecting the sexual partner. There is a need for treatments that are not systemically absorbed and also minimize systemic or local adverse effects and are compatible with prophylactic devices such as condoms.
Some recognized difficulties with treatment of BV are that current antibiotic treatment does not always distinguish between the bacteria normally present in healthy vaginal flora and the infecting anaerobes, and not all anaerobes present are necessarily susceptible to the same antibiotic. There is a need for treatment for BV that has some selectivity for activity against unwanted bacteria and no or low activity against normal vaginal flora. In particular, there is a need for a treatment that reduces the levels of harmful Gram negative bacteria whilst not inhibiting re-establishment of Lactobacillus spp. such as lactic acid-producing or hydrogen peroxide-producing lactobacilli.
Another difficulty is that after treatment, BV often recurs. Based on the results of recent clinical trials, about two thirds of patients suffer from multiple episodes of BV. Since the prevalence of BV in the US is about 30%, this means 20% of women in the US have recurrent BV. Furthermore, recurrent treatment with antibiotics leads to increased incidence of antibiotic resistant bacteria and reduced effectiveness of treatment. There is currently no recommended therapeutic agent approved by the US FDA for prophylaxis of recurrence of BV. There is therefore a need for a therapy for prophylaxis of recurrence of BV.